Thieu Phong was the first reign title, before Dai Tri, of Emperor Tran Du Tong (1341-1369). When Emperor Tran Hien Tong died in 1341, Du Tong was Hien Tong's young brother and was enthroned by his father, the Highest King Tran Minh Tong. Within seventeen years of Thieu Phong, his rule was good because the Highest King was alive to control everything. Under the reign of Thieu Phong, the foreign trade with neighboring countries such as China, Champa, Siam, Java .... began to expand. However, traders and merchant ships were forbidden to enter the Vietnamese main land, except island Van Don, a regular trade port. In this way, the Tran protected the state secrets of Vietnam from foreigners. The Emperor assigned a mandarin to govern and to guard the trade port as well.
The copper Thieu Phong thong bao coin had several varieties, the four characters were written either on clockwise or counter-clockwise direction. Thieu Phong nguyen bao and Thieu Phong binh bao coins were found as well. Thieu Phong binh bao, however had some characteristics as the coins cast in the Trinh Nguyen Lords. There was no record to show that which coin, either thong bao or nguyen bao, cast first.